Silencer for positive pressure gas streams subjected to high amplitude pulsations



Oct. 21, 1958 R. B. BOURNE 2,857,014

SILENCER FOR POSITIVE PRESSURE GAS STREAMS SUBJECTED TO HIGH AMPLITUDEPULSATIONS Filed Nov. 1, 1956 HQ Z /6 28? 2 22 i f 2 3.0 p 24 /2&

INVENTOR. APOAAWA? ,9. aal/RNE ATTOR/VE Y5 I United States PatentSILENCER FOR POSITIVE PRESSURE GAS STREAMS SUBJECTED TO HIGH AMPLI- TUDEPULSATIONS Roland B. Bourne, West Hartford, Conn, assignor to The MaximSilencer Company, Hartford, Conn., a corporation of ConnecticutApplication November 1, 1956, Serial No. 619,799

6 Claims. (Cl. ISL-59) occur if an ordinary silencer is employed. Whilethe discharge pressure of such a blower may be only a few pounds persquare inch, the amplitude and frequency of the pulsations in the airstream, especially when acoustic and mechanical resonances areencountered, can be expected to cause fatigue failure in the ordinarysilencer and/or in the piping or other apparatus associated therewith.

It is the general object of the invention to provide a silencer which isadapted for high acoustic attenuation so as to reduce the amplitude ofthe pulsations in installations of the aforementioned type and which isof such mechanical construction as to withstand the stress encounteredin such installations.

Other, more specific objects of the invention, as well as its features,will become apparent to those skilled in the art from the followingdescription having reference to the attached drawing wherein, by way ofpreferred example only, one specific embodiment'ofthe invention is shownand wherein,

Fig. 1 is a longitudinal cross-sectional view of a silencer constructedin accordance with the present invention; and

Fig. 2 is a transverse cross-sectional view of the silencer taken asindicated by the line 22 of Fig. 1.

In preferred form, a silencer constructed in accordance with thisinvention comprises a generally cylindrical sheet metal shell 10 whichis closed at one end by a transverse header 12 and at the other end by agenerally similar header 14. While the end headers 12 and 14 have beenshown at comprising fiat plates, it will be understood that theseheaders can be curved in the interests of providing greater mechanicalstrength to the construction.

However, fiat plate end headers of the type shown may be used andre-enforced by a plurality of radially extending gussets 16, 16.

The end headers 12 and 14 are further re-enforced and held rigid by alongitudinally extending conduit 18 which is preferably located with itslongitudinal axis on the longitudinal center line of the shell 10. Theconduit 18 is provided to define the main gas and sound conductingchannel within the silencer, and the said conduit is welded or otherwiserigidly secured to one end header 12, which for convenience willhereinafter be referred to as the top end header, and it is also weldedor otherwise rigidly secured in a central opening defined in the otherend header 14. Thus, the top end header 12 closes one end of the conduit18 and the bottom end header 14 embraces the other end of the conduit.The said other end of the conduit is open and in communication with anoutlet fitting 20 which is secured to the bottom end header and which isadapted for connection to a pipe or the like.

The silencer construction is made more rigid or reenforced by aplurality of transverse partitions 22, 24, and 26 each of whichcomprises a sheet metal plate which is welded at its periphery to thegenerally cylindrical shell 10 and which is also welded to the conduit18 at a central opening receiving the said conduit. The interiorpartitions 22, 24 and 26 are spaced along the conduit 18 and shell 10 todefine annular chambers 28, 30, 32 and 34, the chamber 28 being definedbetween the header 12 'and the partition 22, the chamber 30 beingdefined between the partitions 22 and 24, the chamber 32 being definedbetween the partitions 24 and 26 and the chamber 34 being definedbetween the partition 26 and the end header 14. As shown in the drawing,the said transverse partitions are not equally spaced whereby theaforesaid chambers are of different lengths. The purpose of spacing thepartitions to define chambers to different selected lengths will beexplained hereinafter.

One of the chambers, preferably a chamber spaced from an end header, asfor example the chamber 30, is an inlet chamber which receives the airstream from the blower or other source through an inlet fitting 36 whichopens into the side of the shell 10. Preferably, the fitting 36 iswelded to the shell and its connection is made more rigid andre-enforced by a plurality of gussets 38, 38. A plurality of sideopenings 40, 40 are defined in the conduit 18 within the chamber 30 toreceive the air or gas stream therefrom.

It is an important feature of the present invention that the partition22 between the chamber'28 and the inlet chamber 30 is provided with aplurality of circumaxially spaced apertures 42, 42 to effect acousticcommunication and coupling between the said chambers whereby the chamber28 adjacent the end header comprises a closed acoustic sidebranchcommunicating with the inlet chamber 31). It is a further acousticfeature of the present invention that a plurality of apertures 44, 44are provided in the conduit 18 within the chamber 32 whereby to effectacoustic communication and coupling between the main gas and soundconducting channel and the chamber 32, and thus the chamber 32 comprisesa closed acoustic sidebranch communicating with the said channel.Similarly, side openings 46, 46 are provided in the conduit 18 withinthe chamber 34 whereby that chamber also comprises a closed acousticsidebranch communicating with the main sound conducting channel. Theacoustic design and purpose of the closed sidebranches are well known inthe art and need not be explained here. However, it should be noted thatthe inlet chamber 30 and the sidebranch chamber 28 cooperate to providean attenuation surge chamber for incoming pulsations in the streamreceived from the inlet fitting 36. The sidebranch chamber 28 ispreferably sized so as to be tuned to a high harmonic of the fundamentalfrequency of the pulsations anticipated whereby the sidebranch chamber28 will carry less pulsating energy than would be the case if it weretuned to the fundamental frequency. The partition 22 also serves as amechanical shield for the end header 12 whereby to avoid directimpingement on the*said header of the high amplitude -pulsations atfundamental frequency.

it is also preferred that the sidebranch chamber 32 be tuned to thefundamental frequency and the sidebranch chamber 34 be tuned to thesecond harmonic thereof, this in accord with practical acoustic designprinciple. In any event, the sidebranch chambers are large enough andare amply coupled to the main channel so that a continuous band ofattenuation is attained, thereby making it unnecessary to design thesidebranch chambers with great precision as to size.

It has been found that the aforedescribed silencer, in addition toproviding the desired sound attenuation, has the mechanical strengthnecessary to withstand the pulsation energy. In the further interest ofobtaining great mechanical strength, that portion of the shellsurrounding and defining the inlet chamber 313 and the side-- branchchamber 23 is preferably re-enforced with an outer jacket .48 whereby itcan be said that the silencer-shell 10 is of re-enforced laminatedconstruction around the inlet chamber and the sidebranch chamber. Thelaminated construction has been found to reduce shell noise 'due toimpingement of the pulsations in the gas stream and the laminatedconstruction has been found to dampen or reduce low frequency vibrationin the inlet chamber .and the sidebranch chamber.

While the invention has been described with specific reference to apresently preferred embodiment, it will be understood that modificationscan be effected within the scope of the invention as indicated by theclaims which follow.

The invention claimed is:

1. A silencer comprising a generally cylindrical shell, a pair ofheaders closing the ends of the shell, at least one transverse partitiondisposed within said shell to define a plurality of chambers therein,one of the said chambers being an inlet chamber, means defining an inlet,opening in the side of the shell and in communication with the inletchamber and the said partition having at least one opening to eifectacoustic coupling between the inlet chamber and an adjacent one of saidchambers whereby the said adjacent chamber comprises a closed sidebranchacoustically coupled to the inlet chamber, and a main gas and soundconducting conduit located centrally of the'shell and extendinglongitudinally therein through said chambers and said partition with oneend closed by and rigidly connected to one end header and with the otherend rigidly connected to but opening through the other of said endheaders, the said conduit being generally imperforate but having atleast one side opening in said inlet chamber whereby to accommodate gasflow from said inlet chamber.

2. A silencer for gaseous streams comprising a generally cylindricalshell, a pair of headers closing the ends of the shell, a plurality oftransverse partitions disposed within said shell to define at leastthree chambers therewithin, one of said chambers being an inlet chamberand one of the partitions defining said inlet chamber being providedwith at least one opening to provide acoustic coupling between saidinlet chamber and an adjacent one of said chambers whereby the saidadjacent chamber comprises a closed sidebranch acoustically coupled tothe inlet chamber, means defining an inlet opening in the side of theshell and in communication with the inlet chamber, and a main gas andsound conducting conduit located centrally of the shell and extendinglongitudinally therein through all of the said chambers and the saidpartitions and having one end closed by and rigidly connected to one endheader and its other end rigidly connected to but opening through theother end header, the said conduit being generally imperforate buthaving at least one side opening in said inlet chamber to accommodategas flow therefrom and said conduit also being provided with at leastone side opening in another of the said chambers other than the saidacoustic sidebranch to provide acoustic coupling therewith whereby thesaid other chamber comprises a closed sidebranch acoustically coupled tothe conduit.

3. A silencer for gaseous streams comprising a generally cylindricalshell, a pair of headers closing the ends of the shell, a plurality oftransverse partitions disposed within said shell to define at leastthree chambers therewithin in cooperation with each other and with saidend headers, one of the said chambers other than a chamber adjacent anend header comprising an inlet chamber, one of said partitions betweensaid inlet chamber and one of said chambers adjacent an end header beingprovided with at least one opening to effect acoustic coupling betweensaid inlet chamber and the chamber adjacent said end header whereby saidadjacent chamber comprises a closed sidebranch acoustically coupled tothe inlet chamber, means defining an inlet opening in the side of theshell and in communication with the inlet chamber, and a main gas andsound conducting conduit lo cated centrally of the shell and extendinglongitudinally therein through said chambers and said partitions andhaving one end closed by and rigidly connected to one end header and itsother end rigidly connected to but opening through the other end header,the said conduit being generally imperforate but having at least oneside opening in the inlet chamber to accommodate gas flow therefrom andsaid conduit being provided with at least one side opening in another ofsaid chambers other than the inlet chamber and its sidebranch to provideacoustic coupling between said other chamber and said conduit wherebysaid other chamber comprises a closed sidebranch acoustically coupledtothe conduit.

4. A silencer for gaseous streams comprising agenerally cylindricalshell, a pair of headers closing the ends of the shell, a plurality oftransverse partitions disposed within the shell to define at least threechambers therewithin in cooperation with each other and with said endheaders, two of said chambers being end chambers and another of saidchambers being an intermediate chamber, the two end chambers comprisingacoustic sidebranches and said intermediate chamber comprising an inletchamber, the partition separating one end chamber and the inlet chamberbeing provided with at least one opening for acoustic coupling betweenthe said one end chamber and the inlet chamber, means defining an inletopening in said shell in communication with the inlet chamber, and amain gasand sound conducting conduit located centrally of the shell andextending longitudinally therein through said chambers and being rigidlyconnected to said partitions with one end closed by and rigidlyconnected to the oneend header in said one end chamber and with itsother end rigidly connected to but opening through the other end headerin the other end chamber, the said conduit being generally imperforatebut having at least one side opening in the inlet chamber to accommodategas flow therefrom and also being provided with at least one sideopening in said other end chamber to effect-acoustic coupling therewith.

5. A silencer for gaseous streams comprising agenerally cylindricalshell, a pair of headers closing the ends of the shell, threelongitudinally spaced transverse partitions disposed within the shell todefine four chambers therewithin, the said chambers comprising from oneend to the other end of the shell a sidebranch chamber, an inletchamber, and two additional sidebranch chambers, the partitionseparating the first mentioned sidebranch chamber and the inlet chamberbeing provided with at least one opening for acoustic couplingtherebetween, means defining an inlet opening in said shell incommunication with the inlet chamber, and a main gas and soundconducting conduit located centrally of the shell and extendinglongitudinally therein through all of said chambers and being rigidlyconnected to said partitions with one end closed by and rigidlyconnected to the one end header in said first mentioned sidebranchchamber and with its other end rigidly connected to but opening throughthe other end header, the said conduit being generally imperforate buthaving at least one side opening in the inlet chamber to accommodate gas.fiow therefrom and also being provided with at least one side openingin each of the said two additional sidebranch chambers to provideacoustic coupling therewith.

6. A silencer for gaseous streams comprising a generally cylindricalshell, a pair of headers closing the ends of the shell, a plurality oftransverse partitions disposed within the shell to define at least threechambers therewithin in cooperation with each other and with said endheaders, two of said chambers being end chambers and another of saidchambers being an intermediate chamber, the two end chambers comprisingacoustic sidebranches and said intermediate chamber comprising an inletchamber, the partition separating one end chamber and the inlet chamberbeing provided with at least one opening for acoustic coupling betweenthe said one end chamber and the inlet chamber, means defining an inletopening in said shell in communication with the inlet chamber, a maingas and sound conducting conduit located centrally of the shell andextending longitudinally therein through said chambers and being rigidlyconnected to said partitions with one end closed by and rigidlyconnected to the one end header in said one end chamber and with itsother end rigidly connected to but opening through the other end headerin the other end chamber, the said conduit being generally imperforatebut having atleast one side open- References Cited in the file of thispatent UNITED STATES PATENTS 2,138,477 Ludlow Nov. 29, 1938 2,274,459Rauen Feb. 24, 1942 2,277,132 Moss Mar. 24, 1942 2,339,834 Bourne Jan.25, 1944 2,520,756 Bryant Aug. 29, 1950 FOREIGN PATENTS 265 GreatBritain Jan. 5, 1914 (1913) 471,143 France July 2, 1914

